The final phase of a major restoration scheme at Farnham Castle in Surrey has been handed more than £700,000 by the Heritage Lottery Fund (HLF).

Built in 1138 by a grandson of William the Conqueror, Farnham Castle has been designated as a Scheduled Ancient Monument and will now undergo work to open up its history to a wider audience. Funding will be used to complete the much-needed restoration of the main Bishop's Palace, including the castle walls, the Grade II-listed stable block, the gatehouse block and the south range.

The castle's Keep will also be repaired and upgraded with the installation of new interpretation boards and improved safety railings, while it will also be united with the Bishop's Palace under single management for the first time in its 900-year history. A new programme of activities is also set to be implemented at the historic attraction, including a Heritage in Action room to explore the castle's history, a camouflage and illusion scheme to recognise the site's role during the Second World War and one-day courses in stonework.

The scheme is scheduled for completion in spring 2010, with Farnham Castle, which manages the Bishop's Palace, set to take over the running of the Keep from English Heritage in a bid to create a unified vision for future restoration and visitor development. Jane Weeks, chair of the South East England HLF committee, said: "It will repair and conserve one of the few remaining medieval houses of England and introduce new audiences to a long and fascinating history that has something to offer all age groups of local and visiting communities alike."

Jeremy Hunt, member of parliament for South West Surrey, added: "A newly refurbished castle will attract more people to the town and other traders can look forward to benefiting."